Warning lights are universally used on vehicles to alert other drivers and pedestrians to their presence. Vehicles such as trash collection vehicles, mail delivery vehicles, and similar vehicles have particular traffic effects, since they move slowly and stop frequently. Additionally, such vehicles must often be backed-up, for example, to maneuver into and out of dead end streets, parking lots, and the like. Therefore, it is prudent to provide such vehicles with effective warning devices to alert other drivers and pedestrians of their presence. By law, all such vehicles must be provided with tail lights, brake lights, back-up lights, hazard flashers, and, often, back-up sounders. Some localities may also require such vehicles to be provided with additional lights, such as rotating or blinking lights, strobe flashers, or similar auxiliary warning lights.
Auxiliary warning lights for vehicles which operate in a slow-moving and frequently-stopping manner have often been provided as add-on light units which are manually activated and which operate in uncoordinated flashing patterns. Such lights have not usually been wired in with existing warning devices and are, thus, only activated if the driver remembers to activate the lights. However, when such lights are activated, they have usually been effective in alerting others of the presence of the vehicles on which they are installed.
There have been a number of warning light systems which provide multiple warning functions and which are controlled by programmed microprocessors. Most such systems are of the type which are provided as light bar systems, as are used on some police vehicles, fire fighting vehicles, ambulances, and the like. Such systems are capable a selection of light colors and a variety of flash patterns which can be selected by operation of switches mounted on a panel within the vehicle. While such warning light systems are appropriate for emergency response type vehicles, they tend to be expensive and are not really appropriate for the needs of trash pickup trucks and similar vehicles.
In order to provide some coordination with existing warning devices, auxiliary warning lights have been combined with controller units which are interconnected to existing turn signals, backup lights, and the like. The controller unit electrically senses activation of the existing warning lights and causes activation of the auxiliary warning lights in coordination with the existing warning lights. Coordinated auxiliary light combinations of this type have made use of generic vehicle types of lights, usually in combination with separate controller units.
In the past, many types of warning lights, particularly for vehicles, have employed incandescent types of lamps. Although incandescent lamps have provided useful service for illumination and warning lights, there are some negative aspects to incandescent lamps. Incandescent lamps with evacuated glass envelopes are susceptible to breakage. The filaments used in such lamps are also vulnerable to breakage from shocks, vibration, and fatigue over time from thermal expansion and contraction. Incandescent lamps also produce heat by the mechanism through which they produce light, namely electrical resistance.
Other illumination sources besides incandescent lamps have been considered and implemented for both illumination purposes and signaling or warning light purposes, such as ionized gas or gas discharge lights (xenon, halogen, etc.) and solid state lights, including light emitting diodes (LED's). Light emitting diodes are considerably less vulnerable to damage from shock and vibration than incandescent lamps and consume less electrical power for a comparable level of illumination. More recently, light emitting diodes have been developed which can be operated at illumination levels which, in large enough arrays, meet the photometric standards required by regulations and industry standards for vehicle mounted warning lights.
In order to provide coordinated functioning from a pair of auxiliary light units, without the use of an external controller circuit, the coordinated flasher system 900 shown in FIG. 1 was developed. The prior art system 900 is embodied as Model numbers 417, 418, 420, 423, and 794, as manufactured Peterson Manufacturing Company of Grandview, Mo. The system 900 includes light units 902 and 904. Each of the units 902 and 904 includes a light emitting diode (LED) array 906 which is enabled by one or more LED switches or drivers 908, which may be power transistors. The LED switches 908 are, in turn, selectively enabled by a controller or processor 910 mounted internally within each of the light units 902 or 904.
Each controller 910 is connected through switch sensor circuitry 912 to a manually operated cab switch 914 which is mounted in a cab of a vehicle on which the system 900 is installed. The cab switch 914 is connected to the vehicle battery 915 and when closed applies a detectable signal to the switch sensor 912. Additionally, the cab switch 914 is connected internally within the light unit 902 or 904 to the LED switch sets 908 and provide operating power to the LED array 906 when the LED switches 908 are activated. The switch sensor 912 provides level shifting between the battery voltage and the voltage required by the controller 910, which is a programmed microprocessor or microcontroller. Closure of the cab switch 914 is sensed by the controllers 910 through the switch sensor circuits 912. The controllers 910 respond by outputting signals to the LED switch sets 908 to cause each LED array 906 to flash in selected patterns. As thus described, there is no timing coordination between the flash patterns generated by the light units 902 and 904, such that the flash patterns, while defined with respect to a given light unit 902 or 904, are somewhat random with respect to one another. When the cab switch 914 is opened, the flash patterns of the LED arrays 906 cease.
The illustrated flasher system 900 provides coordination between the light units 902 and 904 by the provision of mode communication ports 916 within each unit 902 and 904 and interconnecting the ports 916. The ports 916 are bidirectional serial communication ports interfaced with the controllers 910 and communicate timing and function or mode data between the units 902 and 904. The light units 902 and 904 are provided in two versions—a synchronous version with a synchronous program stored in the controller 910 and an alternating version with an alternating program. If two synchronous versions are combined, the controllers 910 cooperate through the mode communication ports 916 to provide flash patterns which are synchronous. On the other hand, if a synchronous version is combined with an alternating version, the controllers 910 cooperate through the ports 916 to provide a flash pattern which alternates from one light unit 902 to the other unit 904. The data passed by way of the ports 916 enables each controller 910 to detect the program version of the opposite controller 916 without the need to set physical mode switches. The illustrated system 900 does not combine light units 902 and 904 in which both controllers 910 are alternating versions.
Although the system 900 provides coordinated warning light patterns without the need of external controller circuitry, a system which could additionally coordinate with existing warning lights, such as turn signals, hazard flashers, backup signals, and the like, without the need of external controller circuitry is desirable, particularly for slow-moving and frequently-stopping vehicles.